Flexible electric cable



1960 J. L. LYON 2,959,634

' FLEXIBLE ELECTRIC CABLE Filed Nov. 12, 1957 INVENTOR. JAMES L. LYON United States Patent FLEXIBLE ELECTRIC CABLE James L. Lyon, San Jose, Calif., assignor to International Business Machines Corporation, ,New York, N.Y., a

corporation of New York Filed Nov. 12, 1957, Ser. No. 6955809 3 Claims. (Cl. 174-117) The present invention relates to flexible electrical cables. More particularly, the present invention'relates to arrangements wherein two relatively movable'objects are connected by a flexible cable.

When two objects that are subject torapid relative movement are connected by anadequate'length of cable to allow fortheir longest distance of separation, the loose portions of the flexible cable whip and flop "radically in all directions when the objects change their relative position, which is dangerous to attending personnel and may damage adjacent structures. In addition, the repeated rapid bending of thecable on the same or on different radii may cause fatigue of the metal conductors so that they are liable to break after a relatively short time of practical use and thus require replacement. This is costly and interruptsthe operation of the machinery to which it supplies electric power. Such a situation exists in random access accounting machines, such as are described in pendingUS. patent application Serial No. 477,468, filed on December 24, 1954, wherein a flexible cable is connected between a stationary support and a carriage that moves rapidly along a column of superposed magnetic information storage discs to place magnetic transducers into operative relation to selected ones of said discs for the purpose of recording information thereon or collecting information previously recorded on said discs.

It is an object of my invention to provide a simple yet effective arrangement for limiting whipping, flopping and jerking of a cable connected between relatively movable objects that are subject to sudden and rapid changes in their relative position.

Another object of the invention is to provide an arrangement, of the type referred to, by which fatigue of the metallic conductors of the cable is substantially reduced so that the useful life span of the cable is materially extended even under such adverse conditions of use as described above.

Furthermore, it is an object of the present invention to provide, for use between two object that move rapidly relative to each other, a cable structure wherein bending of the cable during relative movement of the objects is confined to a predetermined plane and to a single predetermined radius of sufficient size to avoid fatigue of the metal conductors.

Yet another object of the invention is to provide an electric cable structure that is protected against premature breakage of its metallic conductors when used to connect tworelatively movable objects.

These and other objects of the present invention will be apparent from the following description of the accompanying-drawing which illustrates a preferred embodiment thereof and wherein Figure l is a perspective view, partly in section, of an electric cable structure embodying my invention, showing its components exaggerated in thickness.

Figure 2 is a transverse section through the cable r ice structure shown in Figure l taken along lines2- -2 thereof, and

Figure 3 is a fragmentary perspective view of the translatable access mechanism of a magnetic recording machine that is provided with an electric cable structure embodying my invention.

In accordance with the invention, the metallic conductors it) of a cable (Figures 1 and 2) areembedded in parallel juxtaposition in a flat ribbon 12 of a Eflexible insulating material, and the conductor-containing ribbon is held closely against a flexible metal tape.14 whichhas an arcuate cross section of a predetermined radius r (Figure 2). Said radius is preferably about equal to one-half of the shortest distance d-of approach (Figures 1 and 3) between the relatively movable objects which are connected by the cable structure of the invention. The ribbon 12 and the tape 14 are secured together only at the ends 15 and 16 of thetape 14.by means of arcuate clamps 18 and 20, whose clamping members 18a, 20a and 18b, 2012, respectively, have a radius of curvature corresponding to the radius of curvature of the metal tape, so that the arcuate conformation of the tape is preserved at the points where tape and ribbon are held together; and the ribbon is preferably arranged along the convex outer surface 22 of the tape.

A flexible metal tape of concave cross section has rigidity in all but one direction. It resists any bending effort in edgewise direction, i.e., within a plane determined by its longitudinal edges about an axis normal to said plane, and it also resists any bending effort about a transverse axis in a direction opposite to its concavity, but it will readily bend about a transverse axis in the opposite direction, i.e., in the direction of its concavity along a natural radius R that is about equal to the rad us r of its concavity (Figures 1 and 2). When the conductor-containing ribbon 12 is held closely to the convex side 22 of a tape, of the type described, and is firmly secured to the ends of the tape, the tape acts as va guide for the ribbon and the conductors contained therein, -confining its movements to the movements of the tape, and since the tape will bend only in planes parallel to the plane p which bisects the tape and is parallel to its longitudinal edges (Figures 1 and 2), bending of the conductor-containing ribbon is confined to the same planes so that the ribbon is unable to jerk, flop or lash out laterally when its opposite ends are moved rapidly relatively to each other. Also, since the concave tapewill bend along a predetermined radius only, i.e., a radiusRWhich is about equal to the radius r of its concavity, it is possible by proper choice of the transverse concavity of'the tape to prevent the ribbon from making bends of a sharp ness that will cause the metal conductors embedded therein to develop fatigue prematurely. In this manner the useful life span of the cable may be materially extend ed. Furthermore, since the metal tape14 and the conductor-containing ribbon 12 are only secured to each other at their ends and are therefore free to shift'to'a limited extent relative to each other in a longitudinaldirection when both are bent in unison Within the only plane in which they are able to bend, no strains are set up between the tape and the ribbon when both bend'together about constantly shifting transverse axes during relative movement of the objects to which their ends are secured. As a result thereof, wear of the ribbon is' held at a minimum and the insulation of conductors embedded therein is dependably preserved.

Figure 3 illustrates a mechanism wherein the cable structure of the invention is employed'to advantage. It shows a magnetic information storage device 24 formed by a number of superposed metallic discs '25 that are provided with a magnetizable coating and which are mounted upon a common vertical rotary shaft 26*for rotation therewith. To record information magnetically upon said discs and/or read information previously recorded on selected ones of said discs, it is necessary to bring a magnetic transducer 28 into operative relation with selected tracks on any one of said discs. For this purpose, the transducer is secured to one end of a horizontally disposed arm 32 that is held for slidable movement in a direction radially of the discs in a guide way 34; and the guide way 34, in turn, is mounted upon a carriage 35 Which is arranged to move vertically along the peripheral edges of the discs 25 along a vertical guide post 36. Vertical movement of the carriage to place the transducer opposite a selected disc, and movement of the transducer supporting arm 32 in a direction radially of the selected disc into and out of operative position relative to a selected track of said disc, is effected by a pulley-and-cord mechanism 38 which is driven from a reversible motor (not shown) mounted at the bottom of guide post 36. A transducer positioning arrangement of this type is described in pending US. patent application Serial No. 555,006, filed December 23, 1955, to which reference is made for a more detailed description.

To render the transducer eifective for recording information magnetically upon the discs or for reading selected information previously recorded on said discs, it is necessary to connect a plurality of conductors between the transducer and the electric control circuitry of the recording machine. For this purpose the cable structure of the invention is employed. Its conductors may each comprise a plurality of hair-sized copper wires and the ribbon 12 may consist of a flexible insulating plastic known under the tradename Geon. As previously explained, the ribbon is secured to one end of a steel tape 14 at the convex outer surface 22 thereof by means of arcuate clamping members 18a and 18b of a curvature corresponding to the curvature of the steel tape 14. The tape 14 may be of the type employed in flexible steel rulers. It may be of a thickness of .005 inches and have a true transverse width of A of an inch, and the radius of its concavity may be about 1 inch. The screws 19 of the clamping members 18a, 13b may be employed to secure tape and ribbon to the carriage 35 at a point adjacent the edge 40 of the guide post 36 removed from the discs 25, with the convex side of the tape located adjacent said edge. The conductors 10 protruding from the respective end of the ribbon 12 may then be connected in the proper manner to the transducer 28.

To provide a stationary support for the cable structure 12, 14, whereat its conductors may be appropriately connected to the electric control circuit of the transducer, :1 vertical channel 42 is set up opposite to the guide post 36, and the tape 14 with the ribbon 12 held closely adjacent to its convex surface is bent over an arc of 180 along the natural bending radius R of the steel tape as determined by the radius r of its concavity, and their other ends are clamped ti htly together by the arcuate clamping members 20a and 20b and are secured to the channel 42 near the upper end thereof by means of the screws 21 of said clamping members, such that the cable structure forms a loop of U-shaped conformation having two parallel legs 44a and 44b that lie adjacent the inner face 45 of the channel 4-2 and the edge of the guide post 36 respectively, and are connected by an are 46 that curves along the natural radius R of the steel tape. The conductors projecting from the end of ribbon 12, that is secured to the channel 42, may be twisted into a cable 48 of conventional construction that leads to the control circuitry of the transducer.

When the carriage 35 moves rapidly up and down along the guide post 36 to move the transducer 23 from one selected position to another, the connecting arc of the steel tape will rise or drop, and its leg portions will change in length in the opposite manner, but they will remain in parallel condition relative to each other and to the guide post 36 and channel 42, and the radius along which the connecting arc of the steel tape curves will always remain the same; and due to the manner in which the conductor-containing flexible ribbon 12 is held against and about the convex surface 22 of the steel tape, said ribbon is unable to separate itself from the steel tape; it is guided by and has to follow the controlled movements of said tape. It is, therefore, unable to whip and lash out laterally, and will never bend upon a radius of lesser length than the natural bending radius of the steel tape so that the conductors embedded therein cannot develop metal fatigue for a long time. This is particularly true for those points of the conductors where they emerge from the clamps by which they are secured to the carriage and the supporting channel respectively. At these points the conductors were formerly subjected to the most severe strains and broke frequently after relatively short periods of use, whereas now they are not subjected to any bending strains at these points but are held in a straight position by the two parallel legs of the steel tape. Also, since the ribbon, while forced to cling' to and be guided by the steel tape, is not rigidly connected to said tape except at the opposite ends thereof, no strains are set up between the tape and the ribbon during movement of the carriage, such as would occur owing to their slightly different radii of curvature, if the ribbon and the tape were bonded to each other along their total length. As a result thereof, the ribbon will not crack and the insulation of the conductors is preserved.

While I have explained my invention with the aid of a particular embodiment thereof, it will be understood that the specific constructional details of the invention as shown and described and its place of application are given by way of example only and may be departed from without departing from the scope and spirit of the invention.

I claim:

1. For connection between an object mounted for re versing movement along a rectilinear path and a stationary object located a predetermined distance removed from said path, a self-guiding flexible cable structure comprising a length of self-supporting, flexible guide tape of arcuate cross section with a radius of arcuation equal to about half the shortest distance between said stationary object and said path, the length of said guide tape being greater than said shortest distance, a ribbon of a flexible insulating material disposed adjacent to and extending along the convex surface of said guide tape, said ribbon containing a plurality of thin metallic conductors and being of sufiicient width to spread in a transverse direction over substantially all of said convex tape surface, arcuate clamping means of a curvature corresponding to the transverse curvature of said guide tape clamping said ribbon to said tape only at the opposite ends thereof and securing both said tape and said ribbon to said objects in such a position that the tape with said ribbon held against it forms a loop of U-shaped conformation between said objects with one leg of the U extending parallel and adjacent to said path and the connecting are between the legs of the U being of a radius about equal to the radius of the curvature of the arcuate cross section of said tape.

2. A flexible cable structure comprising a length of a self-supporting flexible guide tape of arcuate cross section; a ribbon of a flexible insulating material containing a plurality of thin longitudinally extending electrical conductors, disposed closely adjacent to and extending longitudinally along the convex surface of said tape independently therefrom, said ribbon being of sufiicient width to spread in a transverse direction over substantially all of said convex tape surface; and means securing said ribbon tightly to said tape only at the opposite ends thereof.

3. A flexible self-guiding cable structure for connecting two relatively movable articles comprising a selfsupporting flexible guide tape of arcuate cross section; a thin ribbon of a flexible insulating material containing a plurality of thin longitudinally extending electrical conductors, disposed closely adjacent to and extending longitudinally along the convex surface of said tape independently therefrom, said ribbon being of sufficient Width to spread in a transverse direction over substantially all of said convex tape surface, and arcuate clamps of a curvature corresponding to the transverse curvature of said arcuate tape holding said ribbon tightly against said tape at only the opposite ends thereof and securing said tape ends to said relatively movable articles.

References Cited in the file of this patent UNITED STATES PATENTS 2,701,818 Tims Feb. 8, 1955 2,835,832 Efromson May 20, 1958 FOREIGN PATENTS 732,501 Great Britain June 22, 1955 763,791 Great Britain Dec. 19, 1956 OTHER REFERENCES Electronics (publication), December 1955, page 313. 

